This invention relates to an apparatus for starting a motor and a furnace and, more particularly, to a furnace recirculating fan starting system which obtains maximum efficiency of the fan motor as the temperature in the furnace increases.
Many commercial driers and heating systems have a furnace which elevates the ambient air to a suitable temperature for drying or heating. Usually such systems employ recirculating fans to continually reheat the furnace atmosphere and to maintain the desired temperature. When the system is first turned on and the furnace is ignited, the recirculating fan receives full power. Since air at lower temperatures is more dense than heated air, the motor which drives the fan is heavily loaded at start-up and the application of full voltage thereto causes belt squeal and other undesirable wear conditions which are common to full voltage starting techniques.
Another technique of starting a furnace system known to the prior art includes permitting a furnace to heat the air in the plenum to its desired temperature and then subsequently starting the recirculating fan when the temperature reaches that desired. This technique reduces the load on the fan motor since the air in the system is warmer, but requires an undesirably long start-up time resulting in delays and general inefficient operation.
Considering such drawbacks, I have developed an apparatus for starting a furnace and a recirculating fan motor which decreases wear on the motor and the linkage which drives the recirculating fan, and attains operating temperatures in a relatively short period of time.